Dutton Bay Tramway - The KATO Underframe

Rolling Stock Construction - The Kato Underframe

Why the KATO underframe?

Many years ago, maybe 1969/70, after dabbling with Eggerbahn and Lilliput HOe (HOn30) stock, predominately 4-wheeled and very basic, we made a decision that bogie rolling stock clearly operates better, and therefore decided to standardize on a fleet of bogie vehicles. We were a little concerned about building these longer vehicles totally from scratch, with difficulties in providing bogie mounts and indeed, the bogies themselves.

A visit to a hobby shop discovered the range of Sekisui Japanese prototype N-scale. In the range of vehicles was an open wagon, a black gondola, which had a girder "fishbelly" underframe. This wagon was coded 801 by the manufacturer. A little study revealed that by simply removing the sides and ends of the open wagon an underframe of 26' (almost 8 metres) in HO was obtained. No other wagon in the range had the same underframe, all the others being modelled on more modern prototypes.

Our search for an underframe suitable for modelling the DBT fleet of bogie vehicles had been satisfied, as in one purchase we had a fully equipped underframe, with bogies and couplers, with no alignment or other construction difficulties.

Kato 8001 This photo shows the current Kato version of the original 801 - now coded as 8001. The only difference we have found is the provision of "standard" N-scale couplers, rather than a version of the HO-scale X2F horn-hook couplers fitted to the Sekisui product.

converted underframe However, the 26 foot length proved to be a little longer than we desired. Although the Victorian Railways 2'6" gauge stock were all built with a length of about 25 feet (7.5 metres), we decided that a length of around 20 feet (6 metres) would be a perfect vehicle size. A further examination of the underframe revealed that removing the central section, basically the horizontal "belly" of the fishbelly girder, left us with a length of almost exactly 20-feet. This was perfect for the models we had in mind, as the photo above of a shortened underframe, awaiting couplers and body, shows.

What about the bogies?

We were also concerned about the use of N-scale bogies on HO-scale vehicles, even though being narrow gauge the prototypical bogies are small and tucked in under the body sides. Over the years we have considered a number of alternative bogies, and as you can see those fitted to the Kato 8001 underframe seem to us to offer a most reasonable appearance, are reliable in operation, and coming with the underframe, obviously are cost-effective.

8001 Bogie The bogie supplied with the 8001 appears to be a friction bearing 'Bettendorf" style. Despite being an "N" scale bogie the wheelbase (measured against the HO scale ruler) is about 3'6", which is quite acceptable for narrow gauge, as is the wheel diameter.

8017 Bogie Bogies fitted to other Kato Japanese goods stock are roller bearing, which are not at all prototypic for narrow gauge. In this example the bogie has come from an 8017 open wagon. As can be seen, the bogie is of much more modern appearance, and is a little smaller, having a wheelbase of less than 3'3"

Atlas Bogie Atlas N-scale bogies appear to be of a similar prototype to the Kato 8001 bogies, but are much smaller, and indeed do look quite tiny under the narrow-gauge vehicles. We have assumed that the difference in physical size of this American "truck" and the Japanese equivalent must be due to them being constructed to varying scales. The US use 1:160 for "N" scale while in Japan it appears as though the scale is more like 1:140. It can be seen that the wheelbase is about 3 feet.

Fox Bogie The wheelbase of the Fox bogies used on the Victorian Railways 2'6" gauge stock is shorter than the Kato bogies, and the wheel diameter is smaller. This photo shows the unpainted white-metal sideframe of an un-built bogie provided by Puffing Billy Models with a kit of an NQR open wagon. The VR narrow gauge stock was all constructed on a common underframe, and all ran on these bogies, whether freight or passenger. These vehicles were all just longer than 20' in length, and although these bogies are lacking their wheelsets the wheelbase can be seen to be 3'3", smaller even than our Kato-8001 standard.

Archbar Bogie These Archbar 2'6" bogies look fine, but have proved extremely difficult to find. The half-dozen or so pairs in use on the DBT have all been obtained from second hand stalls, and indeed we do not even know their derivation. You will notice that the wheelbase is close to 4' on this, designed for HO-scale, bogie.

Body Construction

The bulk of the freight stock on the DBT has been constructed by fabricating styrene sheets and shapes. However, recently Peter has been using polyutherane castings from molds of a Silicone RTV rubber to build the bodies of fleets of wagons. More information on building the fleet of various wagons used on the DBT can be found on the Body Construction Page

Couplers

The Dutton Bay Tramway has standardized on Micro-Trains (Kadee) "N" scale couplers, body mounted. The benefits of these couplers are many, offering a small size and reliable hands-free operation, with automatic coupling and uncoupling (using a magnetic uncoupler), and also the renowned delayed uncoupling feature made famous by the bigger HO scale couplers. Not only that, but their appearance matches the knuckle couplers fitted to the Victorian Railways 2'6" gauge stock. Coincidentally, simply attaching a 1025 coupler to the Kato underframe matches the "N" scale coupler standards exactly.

We also use the little "axle-box" springs provided with the couplers, at the rate of one per normal vehicle, and two per guards van. The effect of these springs is provide a degree of "drag" behind the loco, which tends to keep the couplers stretched. This in turn minimizes the chance of an unexpected uncoupling when passing over a magnet, and also improves the appearance of the train by reducing the bouncing oscillations which appear with the otherwise free-rolling vehicles.

Availability

The only "down side" to using the Kato 8001 as the basis of our vehicles is the availability of the wagons. Here in Australia supply is irregular at best, as it appears as though Kato makes them in relatively small batches. My local hobby store received just two in their latest delivery. We try and retain a stockpile of these wagons to ensure that any requirements for future rolling stock can be met, although there are times when bodies are removed from an underframe in order to allow a required vehicle to be placed in service.

I hope you have enjoyed this short description of the techniques used in constructing the underframe for the "standard" Dutton Bay Tramway goods vehicles.

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Last Modified April 26, 1999

	The bogie supplied with the 8001 appears to be a friction bearing 'Bettendorf" style. Despite being an "N" scale bogie the wheelbase (measured against the HO scale ruler) is about 3'6", which is quite acceptable for narrow gauge, as is the wheel diameter.
	Bogies fitted to other Kato Japanese goods stock are roller bearing, which are not at all prototypic for narrow gauge. In this example the bogie has come from an 8017 open wagon. As can be seen, the bogie is of much more modern appearance, and is a little smaller, having a wheelbase of less than 3'3"
	Atlas N-scale bogies appear to be of a similar prototype to the Kato 8001 bogies, but are much smaller, and indeed do look quite tiny under the narrow-gauge vehicles. We have assumed that the difference in physical size of this American "truck" and the Japanese equivalent must be due to them being constructed to varying scales. The US use 1:160 for "N" scale while in Japan it appears as though the scale is more like 1:140. It can be seen that the wheelbase is about 3 feet.
	The wheelbase of the Fox bogies used on the Victorian Railways 2'6" gauge stock is shorter than the Kato bogies, and the wheel diameter is smaller. This photo shows the unpainted white-metal sideframe of an un-built bogie provided by Puffing Billy Models with a kit of an NQR open wagon. The VR narrow gauge stock was all constructed on a common underframe, and all ran on these bogies, whether freight or passenger. These vehicles were all just longer than 20' in length, and although these bogies are lacking their wheelsets the wheelbase can be seen to be 3'3", smaller even than our Kato-8001 standard.
	These Archbar 2'6" bogies look fine, but have proved extremely difficult to find. The half-dozen or so pairs in use on the DBT have all been obtained from second hand stalls, and indeed we do not even know their derivation. You will notice that the wheelbase is close to 4' on this, designed for HO-scale, bogie.